The present invention relates to a device for monitoring the interior of a conduit.
When a television camera is inserted into a conduit to inspect the wall of the conduit for any damage or cracks that may cause water leakage, it is desirable that the television camera be supported centrally within the conduit. Conventional television cameras for use in conduit inspection have parallel support legs attached to lower and lateral sides of the camera for supporting the camera within the conduit. FIG. 8 of the accompanying drawings is a perspective view of such a prior television camera used for conduit inspection. A television camera 50 shown in FIG. 8 is of box-shaped configuration elongated in the axial direction, and has a monitoring detector 51 on its front end. A cable 52 is led out of the rear end of the television camera 50 up to a television monitoring vehicle on the ground. Inclined leg attachment plates 53 are affixed to the bottom of the television camera 50. A pair of legs 54 are attached to each of the leg attachment plates 53 and support on their distal ends a horizontal support foot 55 having front and rear slider ends 56, 57 for slidable movement through a conduit to be monitored for inspection. The legs on such a television camera are of a fixed length.
It is desirable that the monitoring detector 51 be located on a central axis of the conduit to be monitored. Accordingly, the inside diameter of the conduit with which the television camera can be used is determined. For a different conduit inside diameter, legs of a different length matching that inside diameter should be attached. This requires replacement of the legs 54 and the support feet 55, resulting in a poor efficiency in preparing the television camera for use.
When the television camera 50 while in use in a conduit comes across a varying inside diameter, bumps, recesses, or obstacles in the conduit, the television camera 50 cannot be moved smoothly along since the fixed length of the legs make it difficult for the camera 50 to follow such irregularities in the conduit during advancing movement of the camera.
When the monitoring detector 51 is facing forward, the requirement that the television camera 50 be kept on the central axis of the conduit is less essential. However, since the monitoring detector 51 thus oriented will provide an image of the conduit wall only peripherally around its field of view, it would be difficult to make a detailed localized observation of the conduit wall. It is therefore preferable that the monitoring detector have on its front end a rotatable mirror which rotates about an axis thereof for continuously imaging the wall surface in a direction normal to the axis. A detector with such a rotatable field of view will enable a more detailed inspection of the conduit wall.
A television camera with only two support feet is relatively unstable and is in danger of turning over, since the wall of the conduit is not flat but cylindrical. To avoid such a difficulty, conduit inspection television cameras having four feet have been used. FIG. 9 is a perspective view of a known conduit inspection television camera with four feet. A television camera 60 has a monitoring detector 61 on its front end and a cable 62 on its rear end. Four pairs of front legs 63 and rear legs 64 are fixed to the television camera 60 around its circumference. Support feet 65 are fixed to distal ends of the legs 63, 64.
The television camera 60 shown in FIG. 9 is more stable since it is supported by the four feet. However, it is relatively difficult to support the monitoring detector 61 on a central axis of the conduit being inspected. Further, it is still the case that the legs 63, 64 need to be replaced for conduits of different inside diameters.
The monitoring detectors of these conventional television cameras do not have to be located on the central axis of the conduit if the detectors are directed forwardly. However, in monitoring devices having a monitoring detector facing laterally with its direction of observation rotatable, the detector lens should be spaced a constant distance from the conduit wall at all times for correct pickup and transmission of an image of the conduit wall. If the distance between the lens and mirror of the detector and the inner conduit wall changed during one revolution of the mirror for continuous observation of the inner conduit wall, then the position of the lens would need constant adjustment.
Conventional television cameras for monitoring the interior of a conduit are poor in versatility since they can be used only for those conduits of inside diameters for which they are designed. Further, even when used in a conduit having an optimum inside diameter, the television camera will have difficulty in advancing smoothly due to irregularities such as projections and recesses in the conduit wall.